This game looks and sounds great...
... and probably ranks near the top in those categories for this genre of shooter games. The visual were great, the HUD was well designed, the sound effects and music were good. As a person who would rather have my own music playing while I play the game, I was glad to see a mute and music off options, even if they didn't work great (which I'll cover below).
Unfortunately, this is where the praise stops. This is far from a bad game, don't get me wrong. However, it's not really an exciting game. At the beginning of the game, everything is WAY too slow. The gun fire is slow and it takes many hits to kill the most common red enemy ships. The enemies move pretty slow, and their shots are easy to avoid, they just take forever to kill. The weapon powerup was a nice touch but isn't very useful, it lasts only a short while and doesn't stack if you pick up more than one powerup. The missiles and mines were nice touches as well, but ultimately useless. I didn't need to use them at all and their prices in the shop were definitely not worth buying and using more of them.
Speaking of the shop, another thing that made the game feel SUPER slow was the weapon upgrade. I wasn't able to upgrade my gun for 4 levels, and this was without buying any missiles or mines. Once I did get the upgrade however, the gameplay went from slow and easy to fast and unexciting. The difficulty of the enemies was not on pace with the weapons upgrade. Instead of sitting and taking forever to kill them, I was sitting and killing them too easily, and everything was still moving very slow. '
As I mentioned, the enemies in general were slow and easy to kill/avoid. Another problem with the enemies and the waves they appearing in is that it was repetitive and boring. Red ships would come, then blue circle things would come, then red ships would come, then the purple circles would come, then the green ship would come, etc etc. It was predictable and unexciting on top of being too slow and easy.
Another thing that didn't really take away from gameplay but was annoying that the game didn't "remember" anything. What I mean is that every level started off by showing the controls, even though by the second level I already knew the controls and didn't need to see them. If I had the music muted, when the next level started, it would be muted, and I'd have to do it again, same for sound effects muted, and also for the auto-shoot setting. Also, on the topic of muted sound effects, the rocket ship sound effect after you beat each level would play even if sound was muted.
This game could be improved upon by following the formula of success from many other vertical shooter type games. Generally, having more enemies with less health is more exciting than having more enemies with less health. Also, most shooters of this type have boss battles after every one or two levels, and through the first seven levels of this game I didn't encounter one. This also makes the game much more exciting. As far as gun upgrades go, most players would usually rather have an upgrade system that where you can upgrade your gun after every one or two levels that makes them slightly better, and stays on pace with the difficulty of the enemies, as opposed to having to save four or five levels to buy the next level which is pretty overpowering. A more robust system of upgrades could also be nice, which might include armor or maximum health upgrades. Balance is the key.
In all, a good game, just not a very exciting one, and therefore doesn't hold your attention for very long. With a few improvements this game could potentially be one of the best in the genre.